This invention relates to a method of producing a beam of steel or steel and concrete having a flange, wherein wires having a high elastic limit are mounted on the flange of the steel beam and tension is applied to the wires in order to subject the beam to an upwardly directed flexion. The assembly comprising the flexed beam and tensioned wires may be encased in concrete.
In methods currently employed for producing compressive forces in concrete encasing the portion of the beam which will be subjected to tensile forces under operating stresses, the starting point is a metal beam which by itself must be able to withstand the flexion. Compression in the encasing concrete is obtained by eliminating initial preflexion which was maintained during the setting of the concrete; however, this preflexion gives rise to tensile forces in the encased metal part and therefore produces tensions which are already in the same direction as those which will be produced by operating loads.